JPH082997B2 - Rubber composition containing leather powder and molded article - Google Patents

Description

TECHNICAL FIELD The present invention relates to a leather powder-containing rubber composition and a molded article, and relates to a tennis racket, a badminton racket, a golf club,
Sports goods such as grips for baseball bats, clothing items such as rubber gloves, feathers, hats, handle leather bands, motorcycle handle grips, window frame rubber, wiper rubber, anti-vibration rubber, brake rubber, shift lever It can be used for vehicle grips, vehicle interior parts, vehicle parts such as tires, non-slip members, building materials such as sound absorbing materials, rubber shoes, shoe products such as shoe soles, as well as home appliances, stationery, furniture, musical instruments and the like.

[Background technology]

In recent years, a material (composition) in which synthetic resin and natural leather powder are mixed and integrated as a material that combines the moisture absorption and desorption properties of natural leather with the moist and high-class feel to the strength of artificial leather. Is being developed.

Further, as a technique for mixing and integrating natural leather powder with synthetic rubber, natural rubber, etc., Japanese Patent Laid-Open Nos. 53-121902 and 62-62
No. 252459 is known. These are technologies that impart absorption and moisture release properties that cannot be seen with rubber alone.

[Problems to be Solved by the Invention] However, in the natural leather powder-containing rubber composition and molded article obtained by these techniques, long-term use and storage, especially by leaving for a long time in a humid atmosphere, There is a drawback that white powder is generated on the surface and the product performance and quality (appearance) are deteriorated. In particular, when a natural leather powder having a small particle size, for example, a particle size of 250 μm or less was used, generation of white powder was remarkable.

Further, in the case of producing a grip for sports equipment using a rubber composition containing natural leather powder, if the surface is ground to improve the surface shape, the average particle size of the natural leather powder is small, for example, less than 10 μm. However, the moisture absorption by the leather powder is somewhat inferior, the slip prevention effect is less than that of the same content, and the overall property balance is deteriorated.

An object of the present invention is to provide a leather powder-containing rubber composition and a molded article having excellent long-term performance and quality without generation of white powder.

[Means and Actions for Solving the Problems]

The present invention, in the commercialization of molded articles using a leather powder-containing rubber composition, paying attention to the fact that it is possible to prevent the generation of white powder by using fine leather powder of a small particle size with less impurities,
This is intended to achieve the above object.

The leather powder-containing rubber composition of the present invention has a cortical content of 75 wt% or more, a total amount of water-extractable Na ⁺ ions and Ca ²⁺ ions of 0.5 wt% or less, and an average particle diameter D ₅₀ of 10 μm to. It is composed of a dispersed mixture of 10 to 400 parts by weight of leather powder of 250 μm and 100 parts by weight of rubber.

Further, the leather powder-containing rubber molded article of the present invention is formed mainly using the above-mentioned leather powder-containing rubber composition.

The leather powder-containing rubber composition and the molded article of the present invention are basically rubber powder in which leather powder is dispersed in a sea-island shape.

In this type of composition and molded article, the amounts of leather powder material and rubber material used are 10 to 400 parts by weight and 100 parts by weight, respectively. If the proportion of leather powder exceeds 400 parts by weight, it becomes difficult to knead and stir the composition, and it becomes impossible to uniformly disperse the composition, so that the molded product becomes brittle. On the other hand, if it is less than 10 parts by weight, the effect of its addition, that is, the absorption and moisture releasing properties will be insufficient.

In the composition and molded article of the present invention, the characteristic value of the leather powder is limited for the following reason.

1) Cortical content 75 wt% or more: A high content of cortical content means that the amount of impurities is low, and at the same time improves the surface condition and touch feeling of products mixed in rubber grips, rubber gloves, etc. It is meant to be an important factor. That is, the surface state and the like of the product can be efficiently improved with a smaller amount of powder having a larger cortical content.

2) Total amount of free ions (Na ⁺ , Ca ²⁺ ) that can be extracted with water.
5 wt% or less: Of the impurities derived from leather raw materials, if the amount of free ions extracted with water is large, it will be affected by humidity, heat, etc. when commercialized, and its salts (eg NaCl, Na ₂ So ₄ , CaS
O ₄ etc.) bleed out, leading to a deterioration of the product appearance.

The free ions that can be extracted with water include Na ⁺ and Ca ^2+.
In addition to the anions of Cl ^- and SO ₄ ^2- , there are also anions of Cl ^- and SO ₄ ^2- , but bleeding-out anions are formed only in the form of the salt of the counterion of those ions. ^Is defined as the total amount of Na ⁺ and Ca ²⁺ .

3) Average particle size D ₅₀ = 10 to 250 μm: When the average particle size is less than 10 μm, the water absorption and moisture releasing properties are small,
In particular, when the molded product is polished, it cannot exert a sufficient anti-slip effect. On the other hand, when it exceeds 250 μm, it leads to defects due to poor dispersion and deterioration of surface texture (roughness, unevenness).

When gelatin is used instead of leather powder, the surface is not sticky.

Further, the oil and fat content in the leather powder is related to the odor of the molded article, but the composition and the molded article according to the present invention contain rubber, and because the smell of the comb is considerably strong, the degreasing in the leather powder is Not necessarily required. However, if the oil and fat content in the leather powder is reduced by degreasing, a bad odor caused by the oil and fat content in the leather powder being deteriorated by heat or the like, and the deterioration of the surface texture due to coloring and bleed-out can be reduced, which is preferable. The oil content should be degreased to 2 wt% or less, more preferably 0.5 wt% or less.

 The method for measuring the above characteristic values is as follows.

A) Cortical component: According to JIS K6550-1976 "Leather test method" 6.7.

B) Total amount of free ions (Na, Ca ²⁺ ) extractable with water: 10 g of dried leather powder is stirred in 100 ml of pure water for 24 hours to extract free in from the leather powder. The amount of Na ⁺ and Ca ²⁺ in the extract is determined by atomic absorption spectrometry, and the amount extracted from the leather powder is determined.

C) Average particle size A leather part of several tens of mg is dispersed in 100 ml of methanol, and the particle distribution is measured with a Coulter counter (manufactured by Coulter Electronics Co.) to obtain the average particle size.

The density range of the leather powder measured according to JIS K6721 after the leather powder is dried at 120 ° C. for 2 hours is usually 0.38 g / cc or more. This is because if the density is too low, the leather powder may become fibrous, or a large amount of loose hairs may appear to make it difficult to uniformly disperse the rubber in the rubber.

The leather powder used in the present invention as described above can be obtained, for example, by subjecting the leather powder raw material to coarse pulverization, washing with water, dehydration, swelling treatment with steam, drying and fine pulverization. Then, if necessary, a classification step may be performed to separate the leather powder having an average particle diameter according to the purpose of use. In addition, in order to degrease the leather powder, between the steps of coarse grinding and washing with water,
It suffices to perform steps such as drying, degreasing with a solvent, and removal of residual solvent.

This manufacturing method will be described in more detail. First, in order to facilitate fine pulverization in the subsequent step, the leather powder raw material is coarsely pulverized to a particle size of 10 mm or less by a pulverizer such as a jaw crusher, a cutter mill, a hammer crusher. The roughly crushed leather powder thus obtained usually contains 40 to 60% by weight of water.

As the leather powder raw material, shaving waste leather, floor leather, etc. can be used.

Next, in order to mainly extract and remove free ions (Na ⁺ , Ca ²⁺ ) in the leather and to retain a predetermined water content in the coarse powder, a series of water washing operations including a water washing step and a dehydration step is performed.

A series of water washing operations is effective in a method of repeating several times in a batch system, for example, a certain amount of water is supplied to the crude powder after solvent removal, and after stirring for a desired time and bubbling with air if necessary, dehydration is performed. How to do it depends on the amount of water supplied,
It is usually repeated several times, preferably 3 to 4 times. Dehydration is usually
Although filtration (draining or draining) is carried out from the viewpoint of ease of operation, it may be carried out by another method such as centrifugal dehydration.

It should be noted that the continuous washing operation uses a large amount of water and is not advantageous, but it is possible.

 The water temperature may be room temperature, preferably 30 ° C or lower.

By the above series of washing with water, free Na ⁺ ions and Ca
A water-containing coarse powder having a total amount of ²⁺ ions (dry weight conversion) of 0.5 wt% or less and a water content of 65 to 70% is usually obtained. By this series of water washing operations, the coarse powder finally retains a predetermined water content (65 to 70%).

Therefore, this method only requires confirmation of the water content of the coarse powder after dehydration, and the conventional humidity control step of replenishing the coarse powder after solvent removal with water until the desired water content is achieved. The advantage is that it can be abolished.

Here, the reason why the predetermined amount of water is retained or supplied to the coarse powder is as follows. That is, in the dry state, even if finely pulverized after steam steaming in the next step, pulverization does not proceed. However, when steam-cooking a coarse powder containing water and thus swollen, it is partially heat-denatured, and when it is dried, it becomes tight and hard, and is easily crushed and pulverized.

Next, in order to facilitate the fine pulverization in the subsequent step, swelling treatment (steam steaming) is performed with steam while stirring the coarsely crushed leather powder after dehydration.

Subsequently, in order to facilitate the fine pulverization in the subsequent step, the coarsely crushed leather powder after the swelling treatment is dried until the water content becomes about 3 wt% or less. This drying step is usually performed by combining preliminary drying with a dryer and main drying with a vacuum dryer.

Next, the coarsely crushed leather powder after drying is dried with a dry mill such as a Victory mill, ball mill, colloid mill, jet mill, roller mill, or hammer mill to have an average particle size of 10 μm to 250 μm.
Finely grind until it reaches a certain level.

Then, if necessary, the obtained finely ground leather powder having a wide particle size range is used by a gravity classifier; an inertial classifier; a centrifugal classifier such as a cyclone, a micron separator; a sieving machine, etc. The particles may be classified into various average particle sizes according to the above.

In order to degrease the leather powder, for example, the following next step is added between the steps of coarse pulverization and washing with water.

That is, in order to facilitate degreasing (removal of oil and fat) in a later step, the water-containing coarse powder is dried until the water content becomes about 20 to 30 wt%.

Next, the dried crude powder is degreased with a suitable solvent until the fat and oil content is preferably 2 wt% or less, more preferably 0.5 wt% or less. Here, n-hexane, benzine, methylene chloride, acetone, ethyl acetate, toluene or the like can be used as the degreasing solvent.

Subsequently, in order to remove the residual solvent in the coarse powder, the coarse powder after degreasing is heat-treated. Since steam (steam) is usually used as a heat source for safety reasons, this process is also called steam purge. As other heat source, heated nitrogen, heated air, etc. can be used.

In the above degreasing method, a series of water washing operations are performed after the degreasing step, but this water washing operation can be performed before degreasing or after pulverization.

The rubber used in combination with the leather powder obtained as described above includes diene (butadiene-styrene, butadiene-acrylonitrile), polysulfide (thiochol), olefin (ethylene-propylene, chlorosulfonated polyethylene), There are synthetic rubbers such as organosilicon compound-based, fluorine-containing compound-based, urethane-based, vinyl-based and natural rubbers.

These various synthetic and / or natural rubbers may be used alone or in combination of two or more.

The composition of the present invention contains additives commonly used in this field, such as a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator, depending on the purpose of modification, stabilization of quality, the purpose of use, the use environment. In addition to a sulfur-accelerating aid, a processing aid, a coloring agent such as a dye or a pigment, an ultraviolet absorber, an antiaging agent and the like can be optionally added in necessary amounts.

Here, as the vulcanizing agent, sulfur such as powdered sulfur, insoluble sulfur, surface-treated sulfur and the like; metal oxide such as magnesium oxide, zinc and the like (for CR, CSM, T); quinoid vulcanizing agent;
Peracid vulcanizing agents; amine vulcanizing agents; resin vulcanizing agents; organic sulfur vulcanizing agents and the like.

Examples of the vulcanization accelerator include lead dithiocarbamic acid salt and heterocyclic mercaptan.

Examples of the vulcanization accelerator include zinc white and stearic acid.

Processing aids include stearic acid, polyethylene glycol, paraffin wax and the like.

As the ultraviolet absorber, salicylic acid ester such as phenyl salicylate; benzotriazole such as 2-hydroxyphenyl benzotriazole; 2-hydroxybenzophenone, 2-hydroxy-4-methoxybenzopheon, 2-hydroxy There are hydroxybenzophenone compounds such as -4-octoxybenzophenone and 2,2'-dihydroxy-4-methoxybenzophenone.

As a method for producing the leather powder-containing rubber composition and the molded article of the present invention using the above-mentioned materials, a general mixing method can be used, but the following method may also be used.

The finely cut rubber is melted in advance with a Banbury mixer or the like whose temperature is adjusted to 30 to 60 ° C., and the leather powder is additionally mixed, or both raw materials are simultaneously added to the mixer and mixed.

The mixed product is further made into a sheet by a two-roll at 30 to 40 ° C. to obtain a sheet-shaped molded product, or by pouring or adhering it into a predetermined mold to obtain a molded product having a predetermined shape.

Also, when using liquid rubber, use a stirring blade, etc.
Mix liquid rubber and leather powder.

Here, typical molding methods that can be adopted are injection molding,
Hollow (blown) molding, compression molding, rotational molding, powder slush molding, etc. are available.

Further, for kneading the leather powder and the rubber, an extruder, a kneading roll or the like can be used in addition to the Banbury mixer, and the material of the rubber is not only a cut block but also a pellet, a powder, etc. But it's okay.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.

 First, a method for manufacturing leather powder will be described.

A lump of chrome-tanned cowhide leather (shaving leather) 12
After crushing 00kg into the shape of the original shaving waste leather (max: 1cm width x 12cm length) with a crusher (made by Hosokawa Micron), a coarse crusher (hammer mill made by Odate: capacity 600kg / hr)
Sequentially, to make coarsely crushed leather powder with a particle size of about 10 mm or less.
The water content of this coarse powder was 40 to 60 wt%.

Next, a resin is applied to obtain a better leather powder, and this degreasing was performed as follows.

That is, 350 kg of wet coarse crushed leather powder is put in a vacuum dryer and dried until the water content becomes 20 to 30 wt%. Subsequently, 270 kg of this dried and roughly crushed leather powder was put into a degreasing machine, and while feeding n-hexane at 100 / min, stirring for 1 hour and 15 minutes,
Extract and degrease, then filter. The residual oil and fat content in the obtained defatted coarse powder was 0.5 wt% or less.

Next, the residual solvent of this defatted coarsely crushed leather powder column was heated at 130 ° C, 2 kg /
Purge with cm ² G of steam until the odor of the solvent (hexane) disappears, and complete the degreasing-related steps.

The degreasing machine is replenished with 2 m ² of room temperature water, stirred for 30 minutes, and then drained by filtration. This batch washing operation is carried out four times in total to remove free ions such as metal ions and water-soluble components in the scrap leather. 65-70wt% of coarsely crushed leather powder after filtration and draining
It contained water.

Next, this is transferred to a steam steamer without humidity control, and steamed at 130 ° C. and 2 kg / cm ² G of steam for 45 minutes while stirring.

Next, the steamed coarsely crushed leather powder is pre-dried for 3 hours with a dryer kept at 90 ° C until the water content becomes 30-40wt%, and then dried with a vacuum dryer at 45 ° C for 8 hours to obtain a water content of 1wt. 190 kg of dry coarsely crushed leather powder of not more than% is obtained.

Next, this is finely pulverized at 1700 rpm for 2 hours with a Fine Victory Mill (manufactured by Hosokawa Micron).

Subsequently, this is classified by a cyclone classifier to obtain 35 kg of fine leather powder with an average particle size D ₅₀ = about 30 μm and 155 kg of coarse leather powder with D ₅₀ = about 60 μm.

Manufacture of molded product: Example 1 50 parts by weight of natural rubber (# 3) and 50 parts by weight of synthetic rubber / EPDM (ethylene / pro-lene / diene / methylene linkage; Keltan 314 of Idemitsu DSM Co., Ltd.) each of about 3 cm square block. 50 pieces obtained by cutting into pieces, melting with a Banbury mixer heated to about 40 ° C, and treating as described above
Protein powder having an average particle size of 60 μm was added and mixed in parts by weight of natural leather powder.

The kneaded product is further rolled by a two-roll roll at about 50 ° C to a thickness of 1 cm.
It was formed into a sheet-shaped sheet and naturally cooled.

The mixture sheet was further vulcanized by using two rolls and then pressed at 150 ° C. for 5 minutes to obtain length × width × thickness = 150 mm ×
A 200 mm x 2 mm plate was formed.

For the mixture sheet, the moisture resistance test and the powder drop on the cut surface (leather powder detachment from the molded product) were checked, and the moisture absorption amount and the dynamic friction coefficient were measured for the molded plate, and the surface of the molded plate was polished by about 20 μm. Also, the amount of moisture absorption and the coefficient of dynamic friction were measured.

Example 2 A mixture sheet and a molded product were prepared in the same manner as in Example 1 except that natural leather powder having an average particle size of 30 μm was used during the above-described treatment, in which the steps of drying before degreasing, degreasing and deodorizing with steam were omitted. Was evaluated.

Example 3 As a rubber, synthetic rubber / EPDM (Keiko Idemitsu K.K.
The mixture sheet and the molded product were evaluated in the same manner as in Example 1 except that 100 parts by weight of tan 314) alone was used.

Example 4 The mixture sheet and the molded product were evaluated in the same manner as in Example 1 except that the natural rubber alone was used as 100 parts by weight.

Example 5 Using 80 parts by weight of natural rubber and 20 parts by weight of synthetic rubber / EPDM as rubber, the natural leather powder (average particle size 30 μ
Example 1 was repeated except that 25 parts by weight of m) was used.

Example 6 100 parts by weight of pellet-shaped synthetic rubber (silicone rubber) and 50 parts by weight of the above-treated natural leather powder (average particle size 30 μm) were uniformly mixed with a two-roll roll at 150 ° C. to 160 ° C., A sheet-shaped mixture was obtained, and a sheet-shaped forming plate (150 mm × 150 mm) having a thickness of 2 mm was prepared while heating the sheet-shaped mixture to about 180 ° C. by a press molding machine, and in the same manner as in Example 1. The moisture resistance test, the amount of moisture absorption, and the coefficient of dynamic friction were measured.

Example 7 Example 1 was repeated except that 20 parts by weight of natural rubber, 80 parts by weight of synthetic rubber EPDM, and 350 parts by weight of the natural leather powder (average particle size 60 μm) treated as described above were used.

Comparative Example 1 Natural leather powder that has not been washed with water (average particle size 60μ
All were prepared in the same manner as in Example 1 except that m) was used, and the obtained mixture sheet and molded plate were evaluated.

Comparative Example 2 Natural leather powder that has not been washed with water (average particle size 30μ
Evaluations were performed on the mixture sheet and the molded plate in the same manner as in Example 3 except that m) was used.

Comparative Example 3 A mixture sheet and a molded plate were evaluated in the same manner as in Example 1 except that natural leather powder having a small average particle size (average particle size 5 μm) was used.

Comparative Example 4 A mixture sheet and a molded plate were evaluated in the same manner as in Example 3 except that natural leather powder having a large average particle size (average particle size 300 μm) was used.

Comparative Example 5 To 80 parts by weight of natural rubber and 20 parts by weight of synthetic rubber / EPDM, 450 parts by weight of the same natural leather powder (average particle size 60 μm) as in Example 1 was added. It became difficult to make a sheet.

Comparative Example 6 A small amount of natural leather powder (average particle size 30 μm, 5 parts by weight)
In the same manner as in Example 3 except that was used, the mixture sheet and the molded plate were evaluated.

Comparative Example 7 A small amount of natural leather powder (average particle size 60 μm, 5 parts by weight)
In the same manner as in Example 4 except that was used, the mixture sheet and the molded plate were evaluated.

Comparative Example 8 Instead of natural leather powder, gelatin powder (average particle size 30μ
Evaluation was performed in the same manner as in Example 3 except that a mixed sheet was produced using 50 parts by weight of m) and then a molded plate having a predetermined shape was produced.

Comparative Example 9 80 parts by weight of natural rubber (# 3) and synthetic rubber / EPDM (Kelt
an314) 20 parts by weight was used, and a mixed sheet was prepared without using leather powder. A molded plate was prepared and evaluated in the same manner as in Example 1.

Comparative Example 10 Various evaluations were performed in the same manner as in Example 1 using a molded plate containing 100 parts by weight of synthetic rubber / EPDM (Keltan314).

The compositions and test results in the above Examples and Comparative Examples are shown in Table-1.

As can be seen from Table-1, in Examples 1 to 7, there was no powder drop at the cutter cutting edge (leather powder did not come off from the molded product), and the humidity resistance was left for 24 hours in an atmosphere of 30 ° C and 95% RH. Even in the test, abnormalities such as generation of white powder do not occur. The moisture absorption after standing for 3 hours in an atmosphere of 23 ° C and 80% RH is 3.1 g / cm ² or more for unpolished products and 3.5 g / c for polished products.
It exhibits a value of m ² or more, and can be said to have sufficient hygroscopicity, in other words, moisture release. Further, in the dynamic friction test, the coefficient of dynamic friction was 0.38 kg or more for the unpolished product and 0.45 kg or more for the polished product, which can be said to have a sufficient slip prevention effect. Further, even if the resin of the leather powder is not used as in Example 2, there is no problem in characteristics. However, degreasing is advantageous in terms of odor and the like.

On the other hand, in Comparative Examples 1 and 2, white powder was produced during the moisture resistance test because the leather powder was not washed with water, and in Comparative Example 3, the average particle size of the leather powder was as small as 5 μm, which is less than 10 μm. Both polishing and polishing are low. In addition, Comparative Example 4
Had a large average particle size of leather powder of 300 μm, and thus powder was removed. Further, in Comparative Example 5, since the amount of the leather powder mixed was as large as 450 parts by weight, it was not possible to prepare a sheet, and Comparative Examples 6 and 7
Since the amount of leather powder mixed is as small as 5 parts by weight, the amount of moisture absorption is small and the coefficient of dynamic friction is also small. Further, in Comparative Example 8, gelatin powder was used instead of leather powder, and in Comparative Examples 9 and 10, no leather powder was mixed at all, so that the surface was sticky due to the moisture resistance test. In Comparative Examples 9 and 10, the moisture absorption amount and the dynamic friction coefficient are also small.

From the above results, according to the examples of the present invention, it is possible to prevent the generation of white powder which is observed in the conventional leather powder-containing rubber composition. In addition, it is a rubber molded product containing leather powder that does not have a sticky feeling, and grips such as rackets, handles, writing instruments, and necks of stringed instruments make it difficult to slip when gripped, making it suitable for sports equipment, vehicle parts, stationery, musical instruments, etc. It is possible to add excellent performance. Furthermore, when rubber gloves containing leather powder are used to make clothing gloves, hats, rubber shoes, belts for hanging musical instruments, etc., when sweat occurs in contact with human skin, it does not tend to adhere to the skin. You can easily take it off. In addition, vehicle interior parts using the composition of the present invention,
When a surface material such as a building material, a home electric appliance, or furniture is manufactured, not only a high-quality product with a leather-like appearance is provided, but also a touch feeling is improved.

〔The invention's effect〕

According to the present invention as described above, there is an effect that it is possible to provide a leather powder-containing rubber composition and a molded product which do not generate white powder and have long-term performance and quality excellent in surface properties.

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Claims (2)

[Claims] 1. A water-extractable Na ^{+ having} a cortical content of 75 wt% or more.
Characterized by comprising a dispersed mixture of 10 to 400 parts by weight of leather powder having a total amount of ions and Ca ²⁺ ions of 0.5 wt% or less and an average particle diameter D _{50 of 10} to 250 μm, and 100 parts by weight of rubber. A rubber composition containing leather powder. 2. A leather powder-containing rubber molded article, which is molded mainly using the leather powder-containing rubber composition according to claim 1.